1. Field of the Invention
The present invention relates generally to the fields of medical glues and adhesives. More particularly, it concerns methods and compositions for sealing of wounds and incisions. In certain aspects, the invention concerns adhesion of two or more tissue samples using proteinaceous and/or lipoproteinaceous compositions conjugated and/or mixed with a photosensitizer or dye upon irradiation.
2. Description of Related Art
Healing and sealing tissue wounds remains a problem in medical practice. To enhance tissue healing, much effort has gone towards producing a biocompatible slow release formulation which can be introduced into a tissue defect and that will release biologically active growth factor at a steady rate for the required time. These formulations were designed to promote tissue growth or healing. Examples of these vehicles include biodegradible gelatin hydrogel (Yamamoto et al., 2000), hyaluronan (Mohammad et al., 2000), fibrin glue (Cheng et al., 1998), fibrin derivatives (Sakiyama-Elbert & Hubbell, 2000), alginate microspheres (Nehra et al., 1999), carbopol gel (Sheardown et al., 1997), derivatized dextrans (Tardieu et al., 1992), calcium alginate beads (Downs et al., 1992). It should be noted that many of these slow release vehicles do not actually bind to the tissue, they merely “sit” in the defect and slowly biodegrade. However, a TGF-beta 1 and indocyanine green albumin solder have been used in incisions in pig skin (Poppas et al., 1996). A significant increase in wound healing strength was found using TGF-beta containing solder compared to solder alone.
To replace or promote healing in damaged tissue, various forms of tissue transplants have been conducted. However, cell transplantation often requires that that the donor cells retain their polarity and function, avoid formation of clumps or multilayers, and maintain their viability. In certain tissues, a biodegradable matrix has been used to transplant cells. Three-dimensional cell culture systems with various attachment substrates offer new probabilities for long-term viability and donor cell functions (Wintermantel et al., 1992; Fawcett et al., 1995; Spier and Maroudas, 1991; Peshwa et al., 1996; Rezai et al., 1997; Ruoslahti and Hayman, 1992; Spector et al., 1993; Hoffman, 1994; Kleinman et al., 1998). Successful use of 3-dimensional micro-carriers for transplantation to the liver (Wintermantel et al., 1992) and brain (Fawcett et al., 1995) has been reported by several investigators. In 3-dimensional micro-carriers, the cultured cells are distributed at the outer surfaces and within the body of the particles (Spier and Maroudas, 1991). In a 3-dimensional carrier, more cell contacts are generated compared with a monolayer state, thereby facilitating cell proliferation and spreading (Peshwa et al., 1996; Rezai et al., 1997). The chemistry of the extracellular matrix itself can also modulate various aspects of cell behavior, including adhesion, proliferation, and migration (Ruoslahti and Hayman, 1992).
Successful retinal pigment epithelium (RPE) transplantation requires cell attachment to a substrate prevents RPE apoptosis and de-differentiation after transplantation (Tezel and Del Priore, 1997; Ho et al., 1996). Subretinal provision of RPE cells has been carried out in the form of a cell suspension, RPE patches, or RPE cells grown on artificial substrates (Li and turner, 1991; Sheedlo et al., 1989; Gabrielian et al., 1999; Bhatt et al., 1994). Cell suspension provision has the limitations of reflux from the iatrogenic retinotomy site and irregular distribution of the donor cells in the subretinal space (Wongpichedchai et al., 1992). Retinal pigment epithelium patch grafts, although probably the most physiologic, have not been shown to proliferate in vivo (Gouras et al., 1994; Berglin et al., 1997).
Sealing tissue wounds usually involves sutures and other mechanical seals. Alternative methods to the traditional mechanical means of closing incisions, wounds, and anastomoses have received attention. These may be divided into three groups: first, biological glues (Basu et al., 1995) such as fibrin sealant (Sierra, 1993) and gelatin-resorcinol glue (Albes et al., 1993); second, a technique known as laser tissue welding, which relies on carbon dioxide (Rooke et al., 1993) or Nd:YAG (Back et al., 1994) lasers to produce thermal effects to attach tissue surfaces; and third, chromophore-assisted laser welding (Bass and Treat, 1995) using protein solders that contain a light-absorbing dye together with a laser that emits the appropriate wavelength light. This pairing is most commonly that of fluorescein and a 532-nm frquency-doubled Nd:YAG laser, or indocyanine green and an 805-nm diode laser (Wright and Poppas, 1997).
Alternative tissue adhesives have drawbacks. Cyanoacrylate glues, which have been most frequently used in ophthalmology (Leahey et al., 1993) can be toxic, causing inflammatory reactions and are nonbiodegradable (Siegal and Zaidman, 1989). Fibrin sealants (Spontnitz, 1995) are not particularly effective, form bonds of insufficient strength (Basu et al., 1995; Siedentop et al., 1988), present the possibility of viral infection if prepared from pooled human plasma, and may inhibit would healing (van der Ham et al., 1993). Resorcinol gelatin sealants (Albes et al., 1993) can damage tissue because they contain formaldehyde (Ennker et al., 1994). However, laser-activated tissue solders allows safe preparation and sterilization of the material, because it is activated only under laser illumination and is thought unlikely to lead to tissue toxicity (Bass and Treat, 1995).
Laser tissue welding have been used in urology (Kirsch et al., 1997), vascular surgery (Ashton et al., 1991), neurosurgery (Menovsky et al., 1995), and orthopedics (Forman et al., 1995). Ophthalmologic applications of laser welding with chromophore-assisted protein solder have included sealing cataract incisions (Eaton et al., 1991) and scleral tunnel incisions (Kim et al., 1995) and bonding synthetic epikeratoplasty lenticules to the cornea (Gailitis et al., 1990).
Laser tissue welding without added dye must proceed through a purely thermal mechanism (Schober et al., 1986), whereby the edges of the collagen are partially “unraveled” and can then recombine to form noncovalent bonds (Pearce and Thomsen, 1993). It was thought that dye-assisted welding with protein solders also proceeded through a thermal mechanism, with the chromophore-absorbing energy, releasing it as heat, denaturing the protein in the solder and forming noncovalent bonds between the added protein solder and the tissue collagen (Small et al., 1997). A mixture of cryoprecipitated fibrinogen and a dye that absorbs laser energy and releases it in the form of heat at the wound interface has been used in tissue adhesion (Moazami, et. al., 1990; Oz et al., 1990).
However, results with the two dyes most commonly used for tissue welding, fluorescein and indocyanine green, have produced evidence that photochemical processes occur as well. It has been reported that fluoresceindextran in the rat mesentery lymphatics when illuminated produce changes that could be attributed to singlet oxygen (Zhang et al., 1997). Studies with indocyanine green in vitro have shown that it has a triplet yield of 0.11, and singlet oxygen can be detected by time-resolved luminescence techniques (Baumier et al., 1997; Fickweller et al., 1997). Laser welding with a biologic tissue glue consisting of 18% fibrinogen with 2.6 mg/ml r-5-P showed reduction of the weld strength in the presence of azide which is evidence of singlet oxygen involvement in the weld formation (Khadem et al, 1994).
These chemicals that cause photo-oxidative effects when exposed to visible light have been called “photosensitizers” (Chacon et al., 1988; Tanielian C., 1986; Foote, C. S., 1976). There are two main classes of photosensitizer: tetrapyrroles including porphyrins, chlorins, bacteriochlorins, phthalocyanines, naphthalocyanines, texaphyrins, verdins, purpurins, pheophorbides, etc; and non-tetrapyrrole dyes including flavins, xanthenes, thiazines, selenium and tellurium analogues of thiazines, azines, triarylmethanes, etc. Fluorescein is a xanthene but is not considered a photosensitizer because it releases absorbed energy primarily in the form of heat and fluorescence. Some of these dyes have been evaluated with proteins as tissue glues with varying success (U.S. Pat. No. 5,552,452).
Chlorine6 (Ce6) has been investigated as a photosensitizer for photodynamic therapy both as the free dye (Kostenich et al, 1994) and conjugated to proteins, (Schmidt-Erfurth et al., 1997), macromolecules (Soukos et al., 1997) and particles (Bachor et al., 1991). Covalent conjugates between Ce6 and monoclonal antibodies (Hamblin et al, 1996) and poly-L-amino acids (Soukos et al., 1997) for the photodynamic therapy of cancer have been described. Ce6 is usually thought to act as a photosensitizer by transferring energy from the triplet state to the ground state of molecular oxygen, producing the exited singlet oxygen molecule, a process known as type II photosensitization (Ochsner, 1997). Singlet oxygen can then react with certain amino acids in proteins, particularly histidine, tryptophan, tyrosine, cysteine, and methionine (Dubbelman et al., 1978). One mechanism that has been elucidated for the formation of intermolecular protein cross-links is the reaction of oxidized histidine with free amino groups of lysines on neighboring proteins (Verweij et al., 1981), but it is recognized that other mechanisms must operate as well. There is another possible photo-oxidation pathway involving electron transfer from the photosensitizer triplet state producing either a radical cation or a radical anion, which is known as type I photosensitization (Zhang and Xu, 1994). These radical ions can then react further with oxygen producing carbon and oxygen centered radicals and superoxide anions (Laustrait, 1986). A mechanism for the radical mediated cross-linking of proteins involves the formation of dityrosine (Gill et al., 1997) by phenolic coupling of tyrosine residues on neighboring chains.
Despite these advances in the understanding of tissue healing, tissue transplantation and tissue welding mechanisms, their exists a need for improved methods to heal, transplant and/or weld tissue. Improved methods to promote tissue healing or aid in successful tissue transplants would provide significant benefits in the art. Tissue welds with improved strength would resist tearing under stress. Additionally, there exists a need for methods and compositions of tissue welding, wound healing and tissue transplantation that are easy to handle during surgery, and possess a reduced toxicity or scaring potential.